Conventionally, π conjugated polymers and σ conjugated polymers have been known as organic EL materials which are used to construct the light-emitting layers of organic EL elements.
Polymers represented by poly(paraphenylenevinylene)s (PPV), poly(paraphenylene)s (PPP) and the like are widely utilized as π conjugated polymers. Among such π conjugated polymers, poly(9,9-dialkylfluorene)s (PDAF) have actually been used as polymers that show blue light emission (Y. Ohmori et al., Jpn. J. Appl. Phys., 1991, 30, L1941).
Furthermore, the use of polysilanes (Japanese Patent Application Laid-Open No. 9-78060), polysiloles (S. Yamaguchi et al., Chem. Eur. J., 2000, 6, 1683) and the like as σ conjugated polymers has also been proposed.
Furthermore, polymers comprising fluorene derivative units (π conjugated system) and diarylenesilane derivative units (σ conjugated system) have also been proposed as π-σ conjugated polymers that have a π conjugated system and a σ conjugated system in a single molecule (Japanese Patent Application Laid-Open No. 2001-55447).
However, in the case of π conjugated polymers, the following problem has been encountered: namely, the conjugate length system becomes long when the degree of polymerization increases; as a result, the HOMO-LUMO energy gap (Eg) becomes small, so that the emitted light is shifted toward the red end. Especially in the case of blue light-emitting polymers, the problem of a deterioration in the color purity has been encountered. Furthermore, since the proportion of aromatic rings in π conjugated polymers is extremely high, it cannot be said that the solubility of such polymers in organic solvents is sufficient; as a result, the following problem has also been encountered: specifically, there are cases in which simple film forming methods such as spin coating and the like cannot be used.
Furthermore, in the case of σ conjugated polymers, the electron transporting ability and electron injection ability of polymers are insufficient even though Hall mobility is large.
Meanwhile, in the case of π-σ conjugated polymers, although the drawbacks of σ conjugated polymers can generally be ameliorated, blue emitted light with a high color purity still cannot be obtained.
Objects of the present invention include the provision of a novel π-σ conjugated polymer in which the color purity of blue emitted light in particular is extremely high, the provision of a novel raw material for the manufacture of this π-σ conjugated polymer, and the provision of an organic EL element which uses this π-σ conjugated polymer.